I'm not sure how it could be done visually to make the thor free to move during the attack. That being said, any damage-dealing abilities provide assists in FFA, which earn you 1 mineral (scoring a kill gives 2), so it's not completely useless.

I like the way strike cannons work--I think the fact that it makes you stationary but you have defense matrix to protect you is a good dynamic, so I'll probably keep it as is for now.

A little side-trivia, the roach's hostage ability was originally the roach himself grabbing a victim, but I changed it to a helper roach when I started working on FFA mode because it was a useless ability without teammates.